Placental glucose transport and GLUT 1 expression in insulin-dependent diabetes

METTL3 regulates glucose transporter expression in placenta exposed to hyperglycemia through the mTOR signaling pathway

BACKGROUND

Alterations in the placental expression of glucose transporters (GLUTs), the crucial maternal-fetal nutrient transporters, have been found in women with hyperglycemia in pregnancy (HIP). However, there is still uncertainty about the underlying effect of the high-glucose environment on placental GLUTs expression in HIP.

METHODS

We quantitatively evaluated the activity of mammalian target of rapamycin (mTOR) and expression of GLUTs (GLUT1, GLUT3, and GLUT4) in the placenta of women with normal pregnancies (CTRL, n = 12) and pregnant women complicated with poorly controlled type 2 diabetes mellitus (T2DM, n = 12) by immunohistochemistry. In addition, BeWo cells were treated with different glucose concentrations to verify the regulation of hyperglycemia. Then, changes in the expression of GLUTs following the activation or suppression of the mTOR pathway were also assessed using MHY1485/rapamycin (RAPA) treatment or small interfering RNA (siRNA)-mediated silencing approaches. Moreover, we further explored the alteration and potential upstream regulatory role of methyltransferase-like 3 (METTL3) when exposed to hyperglycemia.

RESULTS

mTOR, phosphorylated mTOR (p-mTOR), and GLUT1 protein levels were upregulated in the placenta of women with T2DM compared with those CTRL. In BeWo cells, mTOR activity increased with increasing glucose concentration, and the expression of GLUT1, GLUT3, and GLUT4 as well as GLUT1 cell membrane translocation were upregulated by hyperglycemia to varying degrees. Both the drug-mediated and genetic depletion of mTOR signaling in BeWo cells suppressed GLUTs expression, whereas MHY1485-induced mTOR activation upregulated GLUTs expression. Additionally, high glucose levels upregulated METTL3 expression and nuclear translocation, and decreasing METTL3 levels suppressed GLUTs expression and mTOR activity and vice versa . Furthermore, in METTL3 knockdown BeWo cells, the inhibitory effect on GLUTs expression was eliminated by activating the mTOR signaling pathway using MHY1485.

CONCLUSION

High-glucose environment-induced upregulation of METTL3 in trophoblasts regulates the expression of GLUTs through mTOR signaling, contributing to disordered nutrient transport in women with HIP.

Glycolysis: A fork in the path of normal and pathological pregnancy

Glucose metabolism is vital to the survival of living organisms. Since the discovery of the Warburg effect in the 1920s, glycolysis has become a major research area in the field of metabolism. Glycolysis has been extensively studied in the field of cancer and is considered as a promising therapeutic target. However, research on the role of glycolysis in pregnancy is limited. Recent evidence suggests that blastocysts, trophoblasts, decidua, and tumors all acquire metabolic energy at specific stages in a highly similar manner. Glycolysis, carefully controlled throughout pregnancy, maintains a dynamic and coordinated state, so as to maintain the homeostasis of the maternal-fetal interface and ensure normal gestation. In the present review, we investigate metabolic remodeling and the selective propensity of the embryo and placenta for glycolysis. We then address dysregulated glycolysis that occurs in the cellular interactive network at the maternal-fetal interface in miscarriage, preeclampsia, fetal growth restriction, and gestational diabetes mellitus. We provide new insights into the field of maternal-fetal medicine from a metabolic perspective, thus revealing the mystery of human pregnancy.

Altered expression of nutrient transporters in syncytiotrophoblast membranes in preeclampsia placentae

INTRODUCTION

Expression of nutrient transporters in the placenta affects fetal growth. This study reports the protein expression of nutrient transporters in the syncytial membranes [microvillous membrane (MVM) and basal membrane (BM)] of normotensive control and preeclampsia placentae.

METHODS

Placentae were collected from fourteen normotensive control women and fourteen women with preeclampsia. The syncytiotrophoblast MVM and BM membranes were isolated. The protein expression of glucose transporter (GLUT1), vitamin B₁₂ transporter (CD320) and fatty acid transporters (FATP2, FATP4) was assessed in both the membranes.

RESULTS

Comparison between membranes demonstrates similar CD320 protein expression in normotensive group whereas, in preeclampsia placentae it was higher in the BM as compared to MVM (p < 0.05). FATP2&4 protein expression was higher in the BM as compared to their respective MVM fraction in both the groups (p < 0.01 for both). Comparison between groups demonstrates higher GLUT1 expression in the MVM (p < 0.05) and BM (p < 0.05) whereas lower CD320 expression in the MVM (p < 0.05) of preeclampsia placentae as compared to their respective membranes in normotensive control. Furthermore, GLUT1 protein expression was positively associated and CD320 protein expression was negatively associated with maternal body mass index (BMI) (p < 0.05 for both). No difference was observed in the FATP2&4 protein expression. However, FATP4 protein expression was negatively associated with maternal blood pressure (p < 0.05 for MVM; p = 0.060 for BM) and birth weight (p < 0.05 for both membranes).

DISCUSSION

The current study for the first time demonstrates differential expression of various transporters in the syncytiotrophoblast membranes of the preeclampsia placentae which may influence fetal growth.

Expression of Glucose Transporters 1 and 3 in the Placenta of Pregnant Women with Gestational Diabetes Mellitus

BACKGROUND

The annual prevalence of gestational diabetes mellitus-characterized by an increase in blood glucose in pregnant women-has been increasing worldwide. The goal of this study was to evaluate the expression of glucose transporter 1 (GLUT1) and glucose transporter 3 (GLUT3) in the placenta of women with gestational diabetes mellitus.

METHODS

Sixty-five placentas from women admitted to the King Saud University Medical City, Riyadh, Saudi Arabia, were analyzed; 34 and 31 placentas were from healthy pregnant women and women with gestational diabetes, respectively. The expressions of GLUT1 and GLUT3 were assessed using RT-PCR, Western blotting, and immunohistochemical methods. The degree of apoptosis in the placental villi was estimated via a TUNEL assay.

RESULTS

The results of the protein expression assays and immunohistochemical staining showed that the levels of GLUT1 and GLUT3 were significantly higher in the placentas of pregnant women with gestational diabetes than those in the placentas of healthy pregnant women. In addition, the findings showed an increase in apoptosis in the placenta of pregnant women with gestational diabetes compared to that in the placenta of healthy pregnant women. However, the results of gene expression assays showed no significant difference between the two groups.

CONCLUSIONS

Based on these results, we conclude that gestational diabetes mellitus leads to an increased incidence of apoptosis in the placental villi and alters the level of GLUT1 and GLUT3 protein expressions in the placenta of women with gestational diabetes. Understanding the conditions in which the fetus develops in the womb of a pregnant woman with gestational diabetes may help researchers understand the underlying causes of the development of chronic diseases later in life.

Effects of Stevioside on the Expressions of GLUT 1, GLUT 3, and GLUT 4 Proteins in Diabetic Rat Placenta

The placenta provides maternal-fetal nutrient transport. The primary source of energy for fetus development is glucose and maternal-fetal glucose transport occurs through glucose transporters (GLUTs). Stevioside, a component of Stevia rebaudiana Bertoni, is used for medicinal and commercial purposes. We aim to determine the effects of stevioside on GLUT 1, GLUT 3, and GLUT 4 proteins expressions in diabetic rat placentas. The rats are divided into four groups. A single dose of streptozotocin (STZ) is administered to form the diabetic groups. Pregnant rats receive stevioside to form the stevioside and diabetic + stevioside groups. According to immunohistochemistry results, GLUT 1 protein is found in both the labyrinth and junctional zones. GLUT 3 protein is limited in the labyrinth zone. GLUT 4 protein is detected in trophoblast cells. According to Western blotting results, on the 15th and 20th days of pregnancy, there is no difference in the expression of GLUT 1 protein between groups. On the 20th day of pregnancy, the expression of GLUT 3 protein in the diabetic group is statistically higher compared to the control group. On the 15th day and 20th day of pregnancy, the expression of GLUT 4 protein in the diabetic group is statistically lower compared to the control group. Insulin levels in blood samples derived from rat abdominal aorta are determined by the ELISA method. According to the ELISA results, there is no difference in insulin protein concentration between groups. Stevioside treatment reduces GLUT 1 protein expression under diabetic conditions.

Placental structure, function, and mitochondrial phenotype relate to fetal size in each fetal sex in mice†

Fetal growth depends on placental function, which requires energy from mitochondria. Here we investigated whether mitochondrial function in the placenta relates to the growth of the lightest and heaviest fetuses of each sex within the litter of mice. Placentas from the lightest and heaviest fetuses were taken to evaluate placenta morphology (stereology), mitochondrial energetics (high-resolution respirometry), mitochondrial regulators, nutrient transporters, hormone handling, and signaling pathways (qPCR and Western blotting). We found that mitochondrial complex I and II oxygen consumption rate was greater for placentas supporting the lightest female fetuses, although placental complex I abundance of the lightest females and complexes III and V of the lightest males were decreased compared to their heaviest counterparts. Expression of mitochondrial biogenesis (Nrf1) and fission (Drp1 and Fis1) genes was lower in the placenta from the lightest females, whilst biogenesis-related gene Tfam was greater in the placenta of the lightest male fetuses. In addition, placental morphology and steroidogenic gene (Cyp17a1 and Cyp11a1) expression were aberrant for the lightest females, but glucose transporter (Slc2a1) expression was lower in only the lightest males versus their heaviest counterparts. Differences in intra-litter placental phenotype were related to changes in the expression of hormone-responsive (androgen receptor) and metabolic signaling (AMPK, AKT, and PPARγ) pathways. Thus, in normal mouse pregnancy, placental structure, function, and mitochondrial phenotype are differentially responsive to the growth of the female and male fetus. This study may inform the design of sex-specific therapies for placental insufficiency and fetal growth abnormalities with life-long benefits for the offspring.

Fetomaternal Expression of Glucose Transporters (GLUTs)-Biochemical, Cellular and Clinical Aspects

Several types of specialized glucose transporters (GLUTs) provide constant glucose transport from the maternal circulation to the developing fetus through the placental barrier from the early stages of pregnancy. GLUT1 is a prominent protein isoform that regulates placental glucose transfer via glucose-facilitated diffusion. The GLUT1 membrane protein density and permeability of the syncytial basal membrane (BM) are the main factors limiting the rate of glucose diffusion in the fetomaternal compartment in physiological conditions. Besides GLUT1, the GLUT3 and GLUT4 isoforms are widely expressed across the human placenta. Numerous medical conditions and molecules, such as hormones, adipokines, and xenobiotics, alter the GLUT's mRNA and protein expression. Diabetes upregulates the BM GLUT's density and promotes fetomaternal glucose transport, leading to excessive fetal growth. However, most studies have found no between-group differences in GLUTs' placental expression in macrosomic and normal control pregnancies. The fetomaternal GLUTs expression may also be influenced by several other conditions, such as chronic hypoxia, preeclampsia, and intrahepatic cholestasis of pregnancy.

Placental Nutrient Transporters and Maternal Fatty Acids in SGA, AGA, and LGA Newborns From Mothers With and Without Obesity

Adverse environmental factors in early life result in fetal metabolic programming and increased risk of adult diseases. Birth weight is an indirect marker of the intrauterine environment, modulated by nutrient availability and placental transport capacity. However, studies of placental transporters in idiopathic birth weight alterations and in maternal obesity in relation to neonatal metabolic outcomes are scarce. We aimed to analyze the placental nutrient transporter protein expression in small (SGA, n = 14), adequate (AGA, n = 18), and large (LGA n = 10) gestational age term for newborns from healthy or obese mothers (LGA-OB, n = 9) and their association with maternal fatty acids, metabolic status, placental triglycerides, and neonatal outcomes. The transporter expression was determined by Western blot. The fatty acid profile was evaluated by gas chromatography, and placental triglycerides were quantified by an enzymatic colorimetric method. GLUT1 was higher in LGA and lower in SGA and positively correlated with maternal HbA1c and placental weight (PW). SNAT2 was lower in SGA, while SNAT4 was lower in LGA-OB. FATP1 was lower in SGA and higher in LGA. SNAT4 correlated negatively and FATP1 correlated positively with the PW and birth anthropometry (BA). Placental triglycerides were higher in LGA and LGA-OB and correlated with pregestational BMI, maternal insulin, and BA. Maternal docosahexaenoic acid (DHA) was higher in SGA, specifically in male placentas, correlating negatively with maternal triglycerides, PW, cord glucose, and abdominal perimeter. Palmitic acid (PA) correlated positively with FATP4 and cord insulin, linoleic acid correlated negatively with PA and maternal cholesterol, and arachidonic acid correlated inversely with maternal TG and directly with FATP4. Our study highlights the importance of placental programming in birth weight both in healthy and obese pregnancies.

Placental expression of glucose transporters GLUT-1, GLUT-3, GLUT-8 and GLUT-12 in pregnancies complicated by gestational and type 1 diabetes mellitus

AIMS/INTRODUCTION

The aim of the present study was to evaluate the placental expression of glucose transporters GLUT-1, GLUT-3, GLUT-8 and GLUT-12 in term pregnancies complicated by well-controlled gestational (GDM) and type 1 pregestational diabetes mellitus (PGDM).

MATERIALS AND METHODS

A total of 103 placental samples were obtained from patients diagnosed with GDM (n = 60), PGDM (n = 20) and a non-diabetic control group (n = 23). Computer-assisted quantitative morphometry of stained placental sections was performed to determine the expression of selected GLUT proteins.

RESULTS

Immunohistochemical techniques used for the identification of GLUT-1, GLUT-3, GLUT-8 and GLUT-12 revealed the presence of all glucose transporters in the placental tissue. Morphometric evaluation performed for the vascular density-matched placental samples demonstrated a significant increase in the expression of GLUT-1 protein in patients with PGDM as compared to GDM and control groups (P < 0.05). With regard to the expression of the other GLUT isoforms, no statistically significant differences were observed between patients from the diabetic and control populations. Positive correlations between fetal birthweight and the expression of GLUT-1 protein in the PGDM group (rho = 0.463, P < 0.05) and GLUT-12 in the control group (rho = 0.481, P < 0.05) were noted.

CONCLUSIONS

In term pregnancies complicated by well-controlled GDM/PGDM, expression of transporters GLUT-3, GLUT-8 and GLUT-12 in the placenta remains unaffected. Increased expression of GLUT-1 among women with type 1 PGDM might contribute to a higher rate of macrosomic fetuses in this population.

Folding of the syncytiotrophoblast basal plasma membrane increases the surface area available for exchange in human placenta

INTRODUCTION

The placental syncytiotrophoblast is the primary barrier between the mother and the fetus. To cross the placenta, nutrients and wastes must be transported across the apical microvillous and basal plasma membranes. While the syncytiotrophoblast basal plasma membrane is typically represented as relatively smooth, it has been shown to have invaginations that may increase its surface area. This study aimed to quantify how folding of the syncytiotrophoblast basal membrane contributes to its surface area and to visualise three-dimensional structures of the basal membrane and cytotrophoblast cell structures.

METHODS

Transmission electron microscope images of human term placenta were analysed using stereological approaches to quantify how folding of the syncytiotrophoblast basal plasma membrane affected surface area. Serial block-face scanning electron microscopy was used to visualise the three-dimensional structure of the syncytiotrophoblast basal membrane and cytotrophoblast cells.

RESULTS

Syncytiotrophoblast basal membrane covered 69.1% of the basal lamina, with cytotrophoblast cells covering the remaining 30.9%. In basal lamina adjacent to syncytiotrophoblast, 34% was adjacent to smooth basal membrane and 66% to folded basal membrane. Syncytiotrophoblast basal membrane folds increased the surface area adjacent to basal lamina by 305%. Including regions overlying the cytotrophoblast cells, basal membrane folds increased syncytiotrophoblast basal membrane surface area by 4.4-fold relative to the basal lamina in terminal villi. Terminal and intermediate villi were similar in terms of trophoblast coverage of the basal lamina and basal membrane folding. The three-dimensional structures of the syncytiotrophoblast basal plasma membrane and cytotrophoblast cells were generated from serial block-face scanning electron microscopy image stacks.

DISCUSSION

These findings indicate that the surface area of the syncytiotrophoblast basal plasma membrane is far larger than had been appreciated. We suggest that these folds increase the surface area available for transport to and from the fetus. Changes in the extent of basal membrane folding could affect nutrient transfer capacity and underlie pathological fetal growth, including fetal growth restriction and macrosomia.

Increased Fetal Cardiovascular Disease Risk: Potential Synergy Between Gestational Diabetes Mellitus and Maternal Hypercholesterolemia

Cardiovascular diseases (CVD) remain a major cause of death worldwide. Evidence suggests that the risk for CVD can increase at the fetal stages due to maternal metabolic diseases, such as gestational diabetes mellitus (GDM) and maternal supraphysiological hypercholesterolemia (MSPH). GDM is a hyperglycemic, inflammatory, and insulin-resistant state that increases plasma levels of free fatty acids and triglycerides, impairs endothelial vascular tone regulation, and due to the increased nutrient transport, exposes the fetus to the altered metabolic conditions of the mother. MSPH involves increased levels of cholesterol (mainly as low-density lipoprotein cholesterol) which also causes endothelial dysfunction and alters nutrient transport to the fetus. Despite that an association has already been established between MSPH and increased CVD risk, however, little is known about the cellular processes underlying this relationship. Our knowledge is further obscured when the simultaneous presentation of MSPH and GDM takes place. In this context, GDM and MSPH may substantially increase fetal CVD risk due to synergistic impairment of placental nutrient transport and endothelial dysfunction. More studies on the separate and/or cumulative role of both processes are warranted to suggest specific treatment options.

FGF15/FGF19 alleviates insulin resistance and upregulates placental IRS1/GLUT expression in pregnant mice fed a high-fat diet

INTRODUCTION

This study aimed to evaluate whether FGF19 can alleviate insulin resistance and change the expression of placental IRS1/GLUTs.

METHODS

Mice transgenic for Fgf15 (the murine homologue of human FGF19) were constructed, and human recombinant FGF19 was administered to pregnant high-fat diet mice. Then, glycolipid metabolism parameters and the weight of foetus and placenta were observed. The expression levels of key molecules of the insulin signalling pathway and glucose transporters in placentae were detected by qRT-PCR and western blotting. Primary trophoblasts and JAR cells were cultured in high-glucose medium, and FGF19 was added to observe its regulatory effects on IRS1/GLUTs.

RESULTS

Overexpressing FGF15 or exogenously administering FGF19 reduced the levels of fasting blood glucose, HOMA-IR, triglycerides, and free fatty acids in pregnant high-fat diet mice compared to control mice (P < 0.05). FGF15/FGF19 did not significantly affect placental weight, foetal weight or litter size (P > 0.05). In addition, FGF15/FGF19 upregulated the expression of p-IRS1 and GLUT4 in the placentae of high-fat diet mice and upregulated GLUT1 levels in the placentae of normal diet-fed mice (P < 0.05), while it did not significantly alter total IRS1 and GLUT3 levels (P > 0.05). Consistent with the results of the animal experiments, FGF19 increased the expression of p-IRS1 and GLUT4 in trophoblast cells cultured in high-glucose medium (P < 0.05).

DISCUSSION

Overexpressing FGF15 or administering FGF19 to pregnant high-fat diet mice can improve glycolipid metabolism and alleviate systemic and local insulin resistance. The possible underlying mechanism may involve upregulation of placental expression of p-IRS1 and GLUT4.

Prenatal exercise in fetal development: a placental perspective

Maternal obesity (MO) and gestational diabetes mellitus (GDM) are common in Western societies, which impair fetal development and predispose offspring to metabolic dysfunction. Placenta is the organ linking the mother to her fetus, and MO suppresses the development of vascular system and expression of nutrient transporters in placenta, thereby affecting fetal development. For maintaining its proper physiological function, placenta is energy demanding, which is met through extensive oxidative phosphorylation. However, the oxidative capacity of placenta is suppressed due to MO and GDM. Recently, several studies showed that physical activity during pregnancy enhances oxidative metabolism and improves placental function, which might be partially mediated by exerkines, referring to cytokines elicited by exercise. In addition, as an endocrine organ, placenta secretes cytokines, termed placentokines, including apelin, superoxide dismutase 3, irisin, and adiponectin, which mediate fetal development and maternal metabolism. Possible molecular mechanisms linking maternal exercise and placentokines to placental and fetal development are further discussed. As an emerging field, up to now, available studies are limited, mostly conducted in rodents. Given the epidemics of obesity and metabolic disorders, as well as the prevalence of maternal sedentary lifestyle, the effects of exercise of pregnant women on placental function and placentokine secretion, as well as their impacts on fetal development, need to be further examined.

Role of Placental Glucose Transporters in Determining Fetal Growth

Maternal nutrient availability and its transport through the placenta are crucial for fetal development. Nutrients are transported to the fetus via specific transporters present on the microvillous (MVM) and basal membrane (BM) of the placenta. Glucose is the most abundant nutrient transferred to the fetus and plays a key role in the fetal growth and development. The transfer of glucose across the human placenta is directly proportional to maternal glucose concentrations, and is mediated by glucose transporter family proteins (GLUTs). Maternal glucose concentration influences expression and activity of GLUTs in the MVM (glucose uptake) and BM (glucose delivery). Alteration in the number and function of these transporters may affect the growth and body composition of the fetus. The thin-fat phenotype of the Indian baby (low ponderal index, high adiposity) is proposed as a harbinger of future metabolic risk. We propose that placental function mediated through nutrient transporters contributes to the phenotype of the baby, specifically that glucose transporters will influence neonatal fat. This review discusses the role of various glucose transporters in the placenta in determining fetal growth and body composition, in light of the above hypothesis.

Effect of type 2 diabetes mellitus on placental expression and activity of nutrient transporters and their association with birth weight and neonatal adiposity

AIMS

Infants born to women with Type 2 Diabetes Mellitus (T2DM) are at risk of being born large for gestational age due to excess fetal fat accretion. Placental nutrient transport determines fetal nutrient availability, impacting fetal growth. The aims of the study were to evaluate the effect of T2DM on placental insulin signaling, placental nutrient transporters and neonatal adiposity.

METHODS

Placentas were collected from BMI-matched normoglycemic controls (NGT, n = 9) and T2DM (n = 9) women. Syncytiotrophoblast microvillous (MVM) and basal (BM) plasma membranes were isolated. Expression of glucose (GLUT1, -4), fatty acid (FATP2, -4, -6, FAT/CD36), amino acid (SNAT1, -2, -4, LAT1, -2) transporters, insulin signaling, and System A transporter activity was determined. Neonatal fat mass (%) was measured in a subset of neonates born to T2DM women.

RESULTS

GLUT1 protein expression was increased (p = 0.001) and GLUT4 decreased (p = 0.006) in BM from T2DM. MVM FATP6 expression was increased (p = 0.02) and correlated with birth weight in both T2DM and NGT groups (r = 0.65, p = 0.02). BM FATP6 expression was increased (p = 0.01) in T2DM. In MVM of T2DM placentas, SNAT1 expression was increased (p = 0.05) and correlated with birth weight (r = 0.84, p = 0.004); SNAT2 was increased (p = 0.01), however System A transporter activity was not different between groups. MVM LAT1 expression was increased (p = 0.01) in T2DM and correlated with birth weight (r = 0.59, p = 0.04) and neonatal fat mass (r = 0.76, p = 0.06).

CONCLUSION

In pregnancies complicated by T2DM placental protein expression of transporters for glucose, amino acids and fatty acids is increased, which may contribute to increased fetal growth and neonatal adiposity.

The role of glucose in physiological and pathological heart formation

Cells display distinct metabolic characteristics depending on its differentiation stage. The fuel type of the cells serves not only as a source of energy but also as a driver of differentiation. Glucose, the primary nutrient to the cells, is a critical regulator of rapidly growing embryos. This metabolic change is a consequence as well as a cause of changes in genetic program. Disturbance of fetal glucose metabolism such as in diabetic pregnancy is associated with congenital heart disease. In utero hyperglycemia impacts the left-right axis establishment, migration of cardiac neural crest cells, conotruncal formation and mesenchymal formation of the cardiac cushion during early embryogenesis and causes cardiac hypertrophy in late fetal stages. In this review, we focus on the role of glucose in cardiogenesis and the molecular mechanisms underlying heart diseases associated with hyperglycemia.

Hyperglycemia and gestational diabetes suppress placental glycolysis and mitochondrial function and alter lipid processing

The degree that maternal glycemia affects placental metabolism of trophoblast cell types [cytotrophoblast (CTB) and syncytiotrophoblast (SCT)] in pregnant persons with gestational diabetes mellitus (GDM) is unknown. We tested the hypotheses that (a) hyperglycemia suppresses the metabolic rates of CTB and SCT; and (b) low placental metabolic activity from GDM placentas is due to decreased oxygen consumption of CTB. Trophoblast cells isolated from GDM and non-GDM term placentas were cultured for 8-hour (CTB) and following syncytialization at 72-hour (SCT) in 5 mM of glucose or 25 mM of glucose. Oxygen consumption rates, glycolysis, ATP levels, and lipid droplet morphometries were determined in CTB and SCT. In CTB from GDM placentas compared to control CTB: (a) oxidative phosphorylation was decreased by 44% (41.8 vs 74.2 pmol O₂ /min/100 ng DNA, P = .002); (b) ATP content was 39% lower (1.1 × 10^-7 vs 1.8 × 10^-7  nM/ng DNA, P = .046); and (c) lipid droplets were two times larger (31.0 vs 14.4 µm² /cell, P < .001) and 1.7 times more numerous (13.5 vs 7.9 lipid droplets/cell, P < .001). Hyperglycemia suppressed CTB glycolysis by 55%-60% (mean difference 20.4 [GDM, P = .008] and 15.4 [non-GDM, P = .029] mpH/min/100 ng DNA). GDM SCT was not metabolically different from non-GDM SCT. However, GDM SCT had significantly decreased expression of genes associated with differentiation including hCG, GCM1, and syncytin-1. We conclude that suppressed metabolic activity by the GDM placenta is attributable to metabolic dysfunction of CTB, not SCT. Critical placental hormone expression and secretion are decreased in GDM trophoblasts.

Complex, coordinated and highly regulated changes in placental signaling and nutrient transport capacity in IUGR

The most common cause of intrauterine growth restriction (IUGR) in the developed world is placental insufficiency, a concept often used synonymously with reduced utero-placental and umbilical blood flows. However, placental insufficiency and IUGR are associated with complex, coordinated and highly regulated changes in placental signaling and nutrient transport including inhibition of insulin and mTOR signaling and down-regulation of specific amino acid transporters, Na+/K+-ATPase, the Na+/H+-exchanger, folate and lactate transporters. In contrast, placental glucose transport capacity is unaltered and Ca2+-ATPase activity and the expression of proteins involved in placental lipid transport are increased in IUGR. These findings are not entirely consistent with the traditional view that the placenta is dysfunctional in IUGR, but rather suggest that the placenta adapts to reduce fetal growth in response to an inability of the mother to allocate resources to the fetus. This new model has implications for the understanding of the mechanisms underpinning IUGR and for the development of intervention strategies.

Expression of placental glucose transporter proteins in pregnancies complicated by fetal growth disorders

During pregnancy fetal growth disorders, including fetal macrosomia and fetal growth restriction (FGR) are associated with numerous maternal-fetal complications, as well as due to the adverse effect of the intrauterine environment lead to an increased morbidity in adult life. Accumulating evidence suggests that occurrence of fetal macrosomia or FGR, may be associated with alterations in the transfer of nutrients across the placenta, in particular of glucose. The placental expression and activity of specific GLUT transporters are the main regulatory factors in the process of maternal-fetal glucose exchange. This review article summarizes the results of previous studies on the expression of GLUT transporters in the placenta, concentrating on human pregnancies complicated by intrauterine fetal growth disorders. Characteristics of each transporter protein found in the placenta is presented, alterations in the location and expression of GLUT isoforms observed in individual placental compartments are described, and the factors regulating the expression of selected GLUT proteins are examined. Based on the above data, the potential function of each GLUT isoform in the maternal-fetal glucose transfer is determined. Further on, a detailed analysis of changes in the expression of glucose transporters in pregnancies complicated by fetal growth disorders is given, and significance of these modifications for the pathogenesis of fetal macrosomia and FGR is discussed. In the final part novel interventional approaches that might reduce the risk associated with abnormalities of intrauterine fetal growth through modifications of placental GLUT-mediated glucose transfer are explored.

In Vivo and In Vitro Models of Diabetes: A Focus on Pregnancy

Diabetes in pregnancy is associated with an increased risk of poor outcomes, both for the mother and her offspring. Although clinical and epidemiological studies are invaluable to assess these outcomes and the effectiveness of potential treatments, there are certain ethical and practical limitations to what can be assessed in human studies.Thus, both in vivo and in vitro models can aid us in the understanding of the mechanisms behind these complications and, in the long run, towards their prevention and treatment. This review summarizes the existing animal and cell models used to mimic diabetes, with a specific focus on the intrauterine environment. Summary of this review.

No evidence of attenuation of placental insulin-stimulated Akt phosphorylation and amino acid transport in maternal obesity and gestational diabetes mellitus

Pregnancies complicated by obesity and/or gestational diabetes (GDM) are associated with peripheral insulin resistance; however, the insulin responsiveness of the placenta in these pregnancy complications remains largely unknown. We tested the hypothesis that primary human trophoblast cells and placental villous explants will be insulin responsive, characterized by amino acid transport, Akt and Erk activity with maternal obesity, and/or GDM. We evaluated term placentas from women with normal body mass index (BMI) (normal; n = 15), obesity (OB; n = 11), normal BMI with GDM (N-GDM; n = 11), and obesity with GDM (OB-GDM; n = 11). In a subgroup, primary human trophoblast cells (PHT) were isolated, and in an independent subgroup placental villous explants were exposed to varying concentrations of insulin. Amino acid transport capacity and insulin signaling activity were determined. Insulin significantly increased amino acid transport activity to a similar degree in PHT cells isolated from normal (+21%), N-GDM (+38%), OB (+37%), and OB-GDM (+35%) pregnancies. Insulin increased Akt and Erk phosphorylation in PHT cells (3-fold) and in villous explants (2-fold) in all groups to a similar degree. In contrast to the peripheral maternal insulin resistance commonly associated with obesity and/or GDM, we found that the placenta is insulin sensitive in these pregnancy complications. We suggest that elevated maternal insulin levels in pregnancies complicated by obesity and/or GDM promote critical placental functions, including amino acid transport. Insulin-stimulated placental nutrient delivery may contribute to the increased risk of fetal overgrowth and adiposity in these pregnancies. Moreover, our findings may inform efforts to optimize insulin regimens for women with GDM.

Mechanism of Placenta Damage in Gestational Diabetes Mellitus by Investigating TXNIP of Patient Samples and Gene Functional Research in Cell Line

INTRODUCTION

Gestational diabetes mellitus (GDM) is a gestational complication that affects maternal and child health. The placenta provides the fetus with the necessary nutrition and oxygen and takes away the metabolic waste. Patients with GDM are diagnosed and treated merely on the basis of the blood glucose level; this approach does nothing to help evaluate the status of the placenta, which is worth noting in GDM. The purpose of this research was to clarify the relation between thioredoxin-interacting protein (TXNIP) and reactive oxygen species (ROS) in the placenta of patients with GDM, which has thus far remained unclear.

METHODS

The expression of TXNIP in the placentas of 10 patients with GDM and 10 healthy puerperae (control group) was investigated via immunofluorescence. The relation among TXNIP, ROS, and the function of mitochondria was explored in HTR-8/SVneo cells stimulated by high glucose (HG).

RESULTS

The results showed the expression of TXNIP in the placentas of patients with GDM was higher than that in the control group, and the expression of TXNIP in HTR-8/SVneo cells treated with HG was higher than that in the control group, causing the accumulation of ROS and changes of mitochondria, promoting apoptosis and inhibition of migration.

CONCLUSIONS

High expression of TXNIP caused by HG mediates the increasing ROS and the mitochondria dysfunction in GDM; this impairs the function of the placenta and is the basis for the prediction of perinatal outcome.

Maternal diet modulates placental nutrient transporter gene expression in a mouse model of diabetic pregnancy

Diabetes in the mother during pregnancy is a risk factor for birth defects and perinatal complications and can affect long-term health of the offspring through developmental programming of susceptibility to metabolic disease. We previously showed that Streptozotocin-induced maternal diabetes in mice is associated with altered cell differentiation and with smaller size of the placenta. Placental size and fetal size were affected by maternal diet in this model, and maternal diet also modulated the risk for neural tube defects. In the present study, we sought to determine the extent to which these effects might be mediated through altered expression of nutrient transporters, specifically glucose and fatty acid transporters in the placenta. Our results demonstrate that expression of several transporters is modulated by both maternal diet and maternal diabetes. Diet was revealed as the more prominent determinant of nutrient transporter expression levels, even in pregnancies with uncontrolled diabetes, consistent with the role of diet in placental and fetal growth. Notably, the largest changes in nutrient transporter expression levels were detected around midgestation time points when the placenta is being formed. These findings place the critical time period for susceptibility to diet exposures earlier than previously appreciated, implying that mechanisms underlying developmental programming can act on placenta formation.

Human placental GLUT1 glucose transporter expression and the fetal insulin-like growth factor axis in pregnancies complicated by diabetes

We have previously described regulation of syncytial GLUT1 glucose transporters by IGF-I. Despite this, it is not clear what signal regulates transplacental glucose transport. In this report we asked whether changes in GLUT1 expression and glucose transport activity in diabetic pregnancies were associated with alterations in the fetal IGF axis. Cord blood samples and paired syncytial microvillous and basal membranes were isolated from normal term pregnancies and pregnancies characterized by gestational diabetes type A2 (GDM A2) and pre-existing insulin-dependent diabetes mellitus (IDDM). Circulating IGF-I, basal membrane GLUT1 expression and glucose transporter activity were correlated with birth weight, but only in control, not diabetic groups. Basal membrane GLUT1 and transporter activity were correlated with IGF-I concentrations in control, but not diabetic groups. IGF binding protein (IGFBP) binding capacity showed a ≥50% reduction in the diabetic groups compared to control; both showed a higher level of free IGF-I. The absence of a correlation between birth weight and factors such as fetal IGF-I or GLUT1 expression in the diabetic groups suggests that IGF-I-stimulated effects may have reached a limiting threshold, such that further increases in IGF-I (or GLUT1) are without effect. These data support that fetal IGF-I acts as a fetal nutritional signal, modulating placental GLUT1 expression and birth weight via altered levels of fetal circulating IGFBPs. Diabetes appears to exert its effects on fetal and placental factors prior to the third trimester and, despite good glycemic control immediately prior to, and in the third trimester, these effects persist to term.

Adipose Tissue Exosomal Proteomic Profile Reveals a Role on Placenta Glucose Metabolism in Gestational Diabetes Mellitus

CONTEXT

Molecules produced by adipose tissue (AT) function as an endocrine link between maternal AT and fetal growth by regulating placental function in normal women and women with gestational diabetes mellitus (GDM).

OBJECTIVE

We hypothesized that AT-derived exosomes (exo-AT) from women with GDM would carry a specific set of proteins that influences glucose metabolism in the placenta.

DESIGN

Exosomes were isolated from omental AT-conditioned media from normal glucose tolerant (NGT) pregnant women (n = 65) and pregnant women with GDM (n = 82). Sequential window acquisition of all theoretical fragment ion spectra mass spectrometry was used to construct a small ion library from AT and exosomal proteins, followed by ingenuity pathway analysis to determine the canonical pathways and biofunctions. The effect of exosomes on human placental cells was determined using a Human Glucose Metabolism RT2 Profiler PCR array.

RESULTS

The number of exosomes (vesicles/μg of tissue/24 hours) was substantially (1.7-fold) greater in GDM than in NGT, and the number of exosomes correlated positively with the birthweight Z score. Ingenuity pathway analysis of the exosomal proteins revealed differential expression of the proteins targeting the sirtuin signaling pathway, oxidative phosphorylation, and mechanistic target of rapamycin signaling pathway in GDM compared with NGT. GDM exo-AT increased the expression of genes associated with glycolysis and gluconeogenesis in placental cells compared with the effect of NGT exo-AT.

CONCLUSIONS

Our findings are consistent with the possibility that AT exosomes play an important role in mediating the changes in placental function in GDM and might be responsible for some of the adverse consequences in this pregnancy complication, such as fetal overgrowth.

A short periconceptional exposure to maternal type-1 diabetes is sufficient to disrupt the feto-placental phenotype in a rabbit model

Tight metabolic control of type-1 diabetes is essential during gestation, but it could be crucial during the periconception period. Feto-placental consequences of maternal type-1 diabetes around the time of conception need to be explored. Using a rabbit model, type-1 diabetes was induced by alloxan 7 days before mating. Glycemia was maintained at 15-20 mmol/L with exogenous insulin injections to prevent ketoacidosis. At 4 days post-conception (dpc), embryos were collected from diabetic (D) or normoglycemic control (C) dams, respectively, and transferred into non-diabetic recipients. At 28dpc, D- and C-feto-placental units were collected for biometry, placental analyses and lipid profiles. D-fetuses were growth-retarded, hyperglycemic and dyslipidemic compared to C-fetuses. The efficiency of D-placentas was associated with an increased gene expression related to nutrient supply and lipid metabolism whereas volume density of fetal vessels decreased. Fetal plasma, placental and fetal liver membranes had specific fatty acid signatures depending on embryonic origin. Tissues from D-fetuses contained more omega-6 polyunsaturated fatty acids. The concentrations of docosahexaenoic acid decreased while linoleic acid increased in the heart of D-fetuses. This study demonstrates that a short exposure to maternal type-1 diabetes in the periconception window, until the blastocyst stage, is able to irreversibly malprogram the feto-placental phenotype, through precocious and persistent structural and molecular adaptations of placenta.

Human placental glucose transport in fetoplacental growth and metabolism

While efficient glucose transport is essential for all cells, in the case of the human placenta, glucose transport requirements are two-fold; provision of glucose for the growing fetus in addition to the supply of glucose required the changing metabolic needs of the placenta itself. The rapidly evolving environment of placental cells over gestation has significant consequences for the development of glucose transport systems. The two-fold transport requirement of the placenta means also that changes in expression will have effects not only for the placenta but also for fetal growth and metabolism. This review will examine the localization, function and evolution of placental glucose transport systems as they are altered with fetal development and the transport and metabolic changes observed in pregnancy pathologies.

Infant of diabetic mother: what one needs to know?

The global incidence of diabetes mellitus, including diabetes in pregnant women, is on the rise. Diabetes mellitus in a pregnant woman jeopardizes not only maternal health but can also have significant implications on the child to be born. Therefore, timely diagnosis and strict glycemic control are of utmost importance in achieving a safe outcome for both the mother and fetus. The treating physician should be aware of the complications that can arise due to poor glycemic control during pregnancy. The objective of this article is to discuss the key concerns in a neonate born to diabetic mother, the underlying pathogenesis, and the screening schedule during pregnancy.

Maternal obesity increases the risk of metabolic disease and impacts renal health in offspring

Obesity, together with insulin resistance, promotes multiple metabolic abnormalities and is strongly associated with an increased risk of chronic disease including type 2 diabetes (T2D), hypertension, cardiovascular disease, non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD). The incidence of obesity continues to rise in astronomical proportions throughout the world and affects all the different stages of the lifespan. Importantly, the proportion of women of reproductive age who are overweight or obese is increasing at an alarming rate and has potential ramifications for offspring health and disease risk. Evidence suggests a strong link between the intrauterine environment and disease programming. The current review will describe the importance of the intrauterine environment in the development of metabolic disease, including kidney disease. It will detail the known mechanisms of fetal programming, including the role of epigenetic modulation. The evidence for the role of maternal obesity in the developmental programming of CKD is derived mostly from our rodent models which will be described. The clinical implication of such findings will also be discussed.

High fructose consumption in pregnancy alters the perinatal environment without increasing metabolic disease in the offspring

Maternal carbohydrate intake is one important determinant of fetal body composition, but whether increased exposure to individual sugars has long-term adverse effects on the offspring is not well established. Therefore, we examined the effect of fructose feeding on the mother, placenta, fetus and her offspring up to 6 months of life when they had been weaned onto a standard rodent diet and not exposed to additional fructose. Dams fed fructose were fatter, had raised plasma insulin and triglycerides from mid-gestation and higher glucose near term. Maternal resistance arteries showed changes in function that could negatively affect regulation of blood pressure and tissue perfusion in the mother and development of the fetus. Fructose feeding had no effect on placental weight or fetal metabolic profiles, but placental gene expression for the glucose transporter GLUT1 was reduced, whereas the abundance of sodium-dependent neutral amino acid transporter-2 was raised. Offspring born to fructose-fed and control dams were similar at birth and had similar post-weaning growth rates, and neither fat mass nor metabolic profiles were affected. In conclusion, raised fructose consumption during reproduction results in pronounced maternal metabolic and vascular effects, but no major detrimental metabolic effects were observed in offspring up to 6 months of age.

Identification of the functional pathways altered by placental cell exposure to high glucose: lessons from the transcript and metabolite interactome

The specific consequences of hyperglycaemia on placental metabolism and function are incompletely understood but likely contribute to poor pregnancy outcomes associated with diabetes mellitus (DM). This study aimed to identify the functional biochemical pathways perturbed by placental exposure to high glucose levels through integrative analysis of the trophoblast transcriptome and metabolome. The human trophoblast cell line, BeWo, was cultured in 5 or 25 mM glucose, as a model of the placenta in DM. Transcriptomic analysis using microarrays, demonstrated 5632 differentially expressed gene transcripts (≥± 1.3 fold change (FC)) following exposure to high glucose. These genes were used to generate interactome models of transcript response using BioGRID (non-inferred network: 2500 nodes (genes) and 10541 protein-protein interactions). Ultra performance-liquid chromatography-mass spectrometry (MS) and gas chromatography-MS analysis of intracellular extracts and culture medium were used to assess the response of metabolite profiles to high glucose concentration. The interactions of altered genes and metabolites were assessed using the MetScape interactome database, resulting in an integrated model of systemic transcriptome (2969 genes) and metabolome (41 metabolites) response within placental cells exposed to high glucose. The functional pathways which demonstrated significant change in response to high glucose included fatty acid β-oxidation, phospholipid metabolism and phosphatidylinositol phosphate signalling.

Effects of Prenatal Nutrition and the Role of the Placenta in Health and Disease

Epidemiologic studies identified the linkage between exposures to stresses, including the type and plane of nutrition in utero with development of disease in later life. Given the critical roles of the placenta in mediating transport of nutrients between the mother and fetus and regulation of maternal metabolism, recent attention has focused on the role of the placenta in mediating the effect of altered nutritional exposures on the development of disease in later life. In this chapter we describe the mechanisms of nutrient transport in the placenta, the influence of placental metabolism on this, and how placental energetics influence placental function in response to a variety of stressors. Further the recent "recognition" that the placenta itself has a sex which affects its function may begin to help elucidate the mechanisms underlying the well-known dimorphism in development of disease in adult life.

DNA methylation of amino acid transporter genes in the human placenta

INTRODUCTION

Placental transfer of amino acids via amino acid transporters is essential for fetal growth. Little is known about the epigenetic regulation of amino acid transporters in placenta. This study investigates the DNA methylation status of amino acid transporters and their expression across gestation in human placenta.

METHODS

BeWo cells were treated with 5-aza-2'-deoxycytidine to inhibit methylation and assess the effects on amino acid transporter gene expression. The DNA methylation levels of amino acid transporter genes in human placenta were determined across gestation using DNA methylation array data. Placental amino acid transporter gene expression across gestation was also analysed using data from publically available Gene Expression Omnibus data sets. The expression levels of these transporters at term were established using RNA sequencing data.

RESULTS

Inhibition of DNA methylation in BeWo cells demonstrated that expression of specific amino acid transporters can be inversely associated with DNA methylation. Amino acid transporters expressed in term placenta generally showed low levels of promoter DNA methylation. Transporters with little or no expression in term placenta tended to be more highly methylated at gene promoter regions. The transporter genes SLC1A2, SLC1A3, SLC1A4, SLC7A5, SLC7A11 and SLC7A10 had significant changes in enhancer DNA methylation across gestation, as well as gene expression changes across gestation.

CONCLUSION

This study implicates DNA methylation in the regulation of amino acid transporter gene expression. However, in human placenta, DNA methylation of these genes remains low across gestation and does not always play an obvious role in regulating gene expression, despite clear evidence for differential expression as gestation proceeds.

Analysis of correlations between the placental expression of glucose transporters GLUT-1, GLUT-4 and GLUT-9 and selected maternal and fetal parameters in pregnancies complicated by diabetes mellitus

PURPOSE

The aim of the study was to analyze the correlations between the expression of glucose transporters GLUT-1, GLUT-4, and GLUT-9 in human term placenta and selected maternal and fetal parameters in pregnancies complicated by diabetes mellitus (DM).

MATERIALS AND METHODS

Placental samples were obtained from healthy control (n = 25) and diabetic pregnancies, including diet-controlled gestational diabetes mellitus (GDMG1) (n = 16), insulin-controlled gestational diabetes mellitus (GDMG2) (n = 6), and pregestational DM (PGDM) (n = 6). Computer-assisted quantitative morphometry of stained placental sections was performed to determine the expression of selected glucose transporter proteins. For the purposes of correlation analysis, the following parameters were selected: type of diabetes, gestational age, maternal prepregnancy body mass index (BMI), gestational weight gain, third trimester glycated hemoglobin concentration, placental weight, fetal birth weight (FBW) as well as ultrasonographic indicators of fetal adiposity, including subscapular (SSFM), abdominal (AFM), and midthigh (MTFM) fat mass measurements.

RESULTS

In the PGDM group, the analysis demonstrated positive correlations between the placental expression of GLUT-1, GLUT-4, and GLUT-9 and FBW, AFM, and SSFM measurements (p < .05). Similarly in the GDMG2 patients positive correlations between GLUT-4 expression, FBW and SSFM were observed (p < .05). In the multivariate regression analysis, only the type of diabetes and FBW were significantly associated with GLUTs expression (p < .001). In addition, maternal prepregnancy BMI significantly contributed to GLUT-1 expression (p < .001).

CONCLUSIONS

The study results revealed that placental expression of GLUT-1, GLUT-4, and GLUT-9 may be involved in the intensification of the fetal growth in pregnancies complicated by GDM/PGDM.

Hypoglycemia in the preterm neonate: etiopathogenesis, diagnosis, management and long-term outcomes

Glucose, like oxygen, is of fundamental importance for any living being and it is the major energy source for the fetus and the neonate during gestation. The placenta ensures a steady supply of glucose to the fetus, while birth marks a sudden change in substrate delivery and a major change in metabolism. Hypoglycemia is one of the most common pathologies encountered in the neonatal intensive care unit and affects a wide range of neonates. Preterm, small for gestational age (GA) and intra-uterine growth restricted neonates are especially vulnerable due to their lack of metabolic reserves and associated co-morbidities. Nearly 30-60% of these high-risk infants are hypoglycemic and require immediate intervention. Preterm neonates are uniquely predisposed to developing hypoglycemia and its associated complications due to their limited glycogen and fat stores, inability to generate new glucose using gluconeogenesis pathways, have higher metabolic demands due to a relatively larger brain size, and are unable to mount a counter-regulatory response to hypoglycemia. In this review we will discuss the epidemiology; pathophysiology; clinical presentation; management and neurodevelopmental outcomes in affected infants and summarize evidence to develop a rational and scientific approach to this common problem.

Glyburide treatment in gestational diabetes is associated with increased placental glucose transporter 1 expression and higher birth weight

Use of glyburide in gestational diabetes (GDM) has raised concerns about fetal and neonatal side effects, including increased birth weight. Placental nutrient transport is a key determinant of fetal growth, however the effect of glyburide on placental nutrient transporters is largely unknown. We hypothesized that glyburide treatment in GDM pregnancies is associated with increased expression of nutrient transporters in the syncytiotrophoblast plasma membranes. We collected placentas from GDM pregnancies who delivered at term and were treated with either diet modification (n = 15) or glyburide (n = 8). Syncytiotrophoblast microvillous (MVM) and basal (BM) plasma membranes were isolated and expression of glucose (glucose transporter 1; GLUT1), amino acid (sodium-coupled neutral amino acid transporter 2; SNAT2 and L-type amino acid transporter 1; LAT1) and fatty acid (fatty acid translocase; FAT/CD36, fatty acid transporter 2 and 4; FATP2, FATP4) transporters was determined by Western blot. Additionally, we determined GLUT1 expression by confocal microscopy in cultured primary human trophoblasts (PHT) after exposure to glyburide. Birth weight was higher in the glyburide-treated group as compared to diet-treated GDM women (3764 ± 126 g vs. 3386 ± 75 g; p < 0.05). GLUT1 expression was increased in both MVM (+50%; p < 0.01) and BM (+75%; p < 0.01). In contrast, MVM FAT/CD36 (-65%; p = 0.01) and FATP2 (-65%; p = 0.02) protein expression was reduced in mothers treated with glyburide. Glyburide increased membrane expression of GLUT1 in a dose-dependent manner in cultured PHT. This data is the first to show that glyburide increases GLUT1 expression in syncytiotrophoblast MVM and BM in GDM pregnancies, and may promote transplacental glucose delivery contributing to fetal overgrowth.

Maternal metabolic adaptations to pregnancy among young women in Cebu, Philippines

OBJECTIVES

Evidence that fetal development has long-term impacts on health has increased interest in maternal-fetal nutrient exchange. Although maternal metabolism is known to change during gestation to accommodate fetal nutrient demands, little is known about these modifications outside of a Western, clinical context. This study characterizes maternal metabolic adaptations to pregnancy, and their associations with offspring birth weight (BW), among women living in the Philippines.

METHODS

Fasting glucose, triglycerides, insulin, leptin, and adiponectin were assessed in 808 participants in the Cebu Longitudinal Health and Nutrition Survey (Metropolitan Cebu, Philippines). Cross-sectional relationships between metabolites and hormones and gestational and lactational status were evaluated. Among the subset of currently pregnant women, associations between maternal glucose and triglycerides and offspring BW were also examined.

RESULTS

Women in their second and third trimesters had significantly lower fasting glucose and adiponectin compared to nulliparous women, and leptin levels and triglyceride levels were notably higher late in pregnancy (all P < .05). Among pregnant women, fasting glucose was a positive predictor of offspring BW, but only in males (P = .012, R²  = .28). Hormones and metabolites in post-partum women trend back toward levels found in nulliparous women, with some differences by breastfeeding status.

CONCLUSIONS

We find evidence for marked changes in maternal lipid and carbohydrate metabolism during pregnancy, consistent with known adaptations to support fetal growth. The finding of sex-specific relationships between maternal glucose and offspring BW adds to evidence for greater impacts of the maternal-gestational environment on biology and health in male offspring.

Impact of pre-gestational and gestational diabetes mellitus on the expression of glucose transporters GLUT-1, GLUT-4 and GLUT-9 in human term placenta

PURPOSE

Various studies in placental tissue suggest that diabetes mellitus alters the expression of glucose transporter (GLUT) proteins, with insulin therapy being a possible modulatory factor. The aim of the present study was quantitative evaluation of the expression of glucose transporters (GLUT-1, GLUT-4, GLUT-9) in the placenta of women in both, uncomplicated and diabetic pregnancy. Additionally, the effect of insulin therapy on the expression of selected glucose transporter isoforms was analyzed.

METHODS

Term placental samples were obtained from healthy control (n = 25) and diabetic pregnancies, including diet-controlled gestational diabetes mellitus (GDMG1) (n = 16), insulin-controlled gestational diabetes mellitus (GDMG2) (n = 6), and pre-gestational diabetes mellitus (PGDM) (n = 6). Computer-assisted quantitative morphometry of stained placental sections was performed to determine the expression of selected glucose transporter proteins.

RESULTS

Morphometric analysis revealed a significant increase in the expression of GLUT-4 and GLUT-9 in insulin-dependent diabetic women (GDMG2 + PGDM) as compared to both, control and GDMG1 groups (p < .05). Significantly increased GLUT-1 expression was observed only in placental specimens from patients with PGDM (p < .05). No statistically significant differences in GLUT expression were found between GDMG1 patients and healthy controls.

CONCLUSIONS

The results of the study confirmed the presence of GLUT-1, GLUT-4 and GLUT-9 proteins in the trophoblast from both, uncomplicated and diabetic pregnancies. In addition, insulin therapy may increase placental expression of GLUT-4 and GLUT-9, and partially GLUT-1, in women with GDMG2/PGDM.

Placental Nutrient Transport in Gestational Diabetic Pregnancies

Maternal obesity during pregnancy is rising and is associated with increased risk of developing gestational diabetes mellitus (GDM), defined as glucose intolerance first diagnosed in pregnancy (1). Fetal growth is determined by the maternal nutrient supply and placental nutrient transfer capacity. GDM-complicated pregnancies are more likely to be complicated by fetal overgrowth or excess adipose deposition in utero. Infants born from GDM mothers have an increased risk of developing cardiovascular and metabolic disorders later in life. Diverse factors, such as ethnicity, age, fetal sex, clinical treatment for glycemic control, gestational weight gain, and body mass index among others, represent a challenge for studying underlying mechanisms in GDM subjects. Determining the individual roles of glucose intolerance, obesity, and other factors on placental function and fetal growth remains a challenge. This review provides an overview of changes in placental macronutrient transport observed in human pregnancies complicated by GDM. Improved knowledge and understanding of the alterations in placenta function that lead to pathological fetal growth will allow for development of new therapeutic interventions and treatments to improve pregnancy outcomes and lifelong health for the mother and her children.

A clinical study which relates to a theoretical simulation of the glucose transport in the human placenta under various diabetic conditions

AIMS

To characterize placental glucose delivery under normoglycemic conditions, gestational and pre-gestational diabetes and to relate the clinical data to theoretical predictions.

METHODS

Data from 125 pregnancies: 50 normal gestations and 75 ones with various types of diabetes were collected. In parallel, we formulated a theoretical model for the transport of glucose under various diabetic conditions. Measured glucose blood levels were fed into the theoretical model that predicts glucose supply to the fetus and the results were confronted with measured fetal weights.

RESULTS

Measured fetal weight and computed glucose delivery in gestational diabetic parturients resemble the situation in normal pregnancies. However, pre-gestational diabetes has a major effect as it involves heavier fetuses and enhanced computed glucose fluxes via placental membranes.

CONCLUSIONS

Fetal weight (increased in pre-gestational and unaltered in gestational diabetes) correlates with the predicted rate of glucose delivery through the placenta.

[Impact of maternal obesity and diabetes on placental function]

Located at the feto-maternal interface, the placenta is involved in exchange, endocrine and immune functions, which impact fetal development. In contact with the maternal environment, this organ is sensitive to metabolic disorders as over-nutrition, obesity or diabetes. The alteration of blood parameters associated with these pathologies affects placental histology, vascularization and nutrient transfers and, according to the types of troubles, induces local inflammation or hypoxia. These placental changes lead to disturbance of development and fetal growth, which increase the risk of pathologies in offspring in adulthood. The placenta thus appears as a crucial player in the fetal programming.

Placental Responses to Changes in the Maternal Environment Determine Fetal Growth

Placental responses to maternal perturbations are complex and remain poorly understood. Altered maternal environment during pregnancy such as hypoxia, stress, obesity, diabetes, toxins, altered nutrition, inflammation, and reduced utero-placental blood flow may influence fetal development, which can predispose to diseases later in life. The placenta being a metabolically active tissue responds to these perturbations by regulating the fetal supply of nutrients and oxygen and secretion of hormones into the maternal and fetal circulation. We have proposed that placental nutrient sensing integrates maternal and fetal nutritional cues with information from intrinsic nutrient sensing signaling pathways to balance fetal demand with the ability of the mother to support pregnancy by regulating maternal physiology, placental growth, and placental nutrient transport. Emerging evidence suggests that the nutrient-sensing signaling pathway mechanistic target of rapamycin (mTOR) plays a central role in this process. Thus, placental nutrient sensing plays a critical role in modulating maternal-fetal resource allocation, thereby affecting fetal growth and the life-long health of the fetus.

Maternal Body Weight and Gestational Diabetes Differentially Influence Placental and Pregnancy Outcomes

CONTEXT

Maternal obesity and gestational diabetes mellitus (GDM) can both contribute to adverse neonatal outcomes. The extent to which this may be mediated by differences in placental metabolism and nutrient transport remains to be determined.

OBJECTIVE

Our objective was to examine whether raised maternal body mass index (BMI) and/or GDM contributed to a resetting of the expression of genes within the placenta that are involved in energy sensing, oxidative stress, inflammation, and metabolic pathways.

METHODS

Pregnant women from Spain were recruited as part of the "Study of Maternal Nutrition and Genetics on the Foetal Adiposity Programming" survey at the first antenatal visit (12-20 weeks of gestation) and stratified according to prepregnancy BMI and the incidence of GDM. At delivery, placenta and cord blood were sampled and newborn anthropometry measured.

RESULTS

Obese women with GDM had higher estimated fetal weight at 34 gestational weeks and a greater risk of preterm deliveries and cesarean section. Birth weight was unaffected by BMI or GDM; however, women who were obese with normal glucose tolerance had increased placental weight and higher plasma glucose and leptin at term. Gene expression for markers of placental energy sensing and oxidative stress, were primarily affected by maternal obesity as mTOR was reduced, whereas SIRT-1 and UCP2 were both upregulated. In placenta from obese women with GDM, gene expression for AMPK was also reduced, whereas the downstream regulator of mTOR, p70S6KB1 was raised.

CONCLUSIONS

Placental gene expression is sensitive to both maternal obesity and GDM which both impact on energy sensing and could modulate the effect of either raised maternal BMI or GDM on birth weight.

Increased placental nutrient transport in a novel mouse model of maternal obesity with fetal overgrowth

OBJECTIVE

To identify possible mechanisms linking obesity in pregnancy to increased fetal adiposity and growth, a unique mouse model of maternal obesity associated with fetal overgrowth was developed, and the hypothesis that maternal obesity causes up-regulation of placental nutrient transporter expression and activity was tested.

METHODS

C57BL/6J female mice were fed a control (C) or a high-fat/high-sugar (HF/HS) pelleted diet supplemented by ad libitum access to sucrose (20%) solution, mated, and studied at embryonic day 18.5.

RESULTS

HF/HS diet increased maternal fat mass by 2.2-fold (P < 0.01) and resulted in glucose intolerance with normal fasting glucose. Maternal circulating insulin, leptin, and cholesterol were increased (P < 0.05) whereas total and high-molecular-weight adiponectin was decreased (P < 0.05). HF/HS diet increased fetal weight (+18%, P = 0.0005). In trophoblast plasma membranes (TPM) isolated from placentas of HF/HS-fed animals, protein expression of glucose transporter (GLUT) 1 and 3, sodium-coupled neutral amino acid transporter (SNAT) 2, and large neutral amino acid transporter 1 (LAT1) was increased. TPM System A and L amino acid transporter activity was increased in the HF/HS group.

CONCLUSIONS

Up-regulation of specific placental nutrient transporter isoforms may constitute a mechanism underlying fetal overgrowth in maternal obesity.

Placenta-on-a-chip: a novel platform to study the biology of the human placenta

OBJECTIVE

Studying the biology of the human placenta represents a major experimental challenge. Although conventional cell culture techniques have been used to study different types of placenta-derived cells, current in vitro models have limitations in recapitulating organ-specific structure and key physiological functions of the placenta. Here we demonstrate that it is possible to leverage microfluidic and microfabrication technologies to develop a microengineered biomimetic model that replicates the architecture and function of the placenta.

MATERIALS AND METHODS

A "Placenta-on-a-Chip" microdevice was created by using a set of soft elastomer-based microfabrication techniques known as soft lithography. This microsystem consisted of two polydimethylsiloxane (PDMS) microfluidic channels separated by a thin extracellular matrix (ECM) membrane. To reproduce the placental barrier in this model, human trophoblasts (JEG-3) and human umbilical vein endothelial cells (HUVECs) were seeded onto the opposite sides of the ECM membrane and cultured under dynamic flow conditions to form confluent epithelial and endothelial layers in close apposition. We tested the physiological function of the microengineered placental barrier by measuring glucose transport across the trophoblast-endothelial interface over time. The permeability of the barrier study was analyzed and compared to that obtained from acellular devices and additional control groups that contained epithelial or endothelial layers alone.

RESULTS

Our microfluidic cell culture system provided a tightly controlled fluidic environment conducive to the proliferation and maintenance of JEG-3 trophoblasts and HUVECs on the ECM scaffold. Prolonged culture in this model produced confluent cellular monolayers on the intervening membrane that together formed the placental barrier. This in vivo-like microarchitecture was also critical for creating a physiologically relevant effective barrier to glucose transport. Quantitative investigation of barrier function was conducted by calculating permeability coefficients and metabolic rates in varying conditions of barrier structure. The rates of glucose transport and metabolism were consistent with previously reported in vivo observations.

CONCLUSION

The "Placenta-on-a-Chip" microdevice described herein provides new opportunities to simulate and analyze critical physiological responses of the placental barrier. This system may be used to address the major limitations of existing placenta model systems and serve to enable research platforms for reproductive biology and medicine.

Increased glucose and placental GLUT-1 in large infants of obese nondiabetic mothers

OBJECTIVE

Obese women are at increased risk to deliver a large infant, however, the underlying mechanisms are poorly understood. Fetal glucose availability is critically dependent on placental transfer and is linked to fetal growth by regulating the release of fetal growth hormones such as insulin. We hypothesized that (1) umbilical vein glucose and insulin levels and (2) placental glucose transporter (GLUT) expression and activity are positively correlated with early pregnancy maternal body mass index and infant birthweight.

STUDY DESIGN

Subjects in this prospective observational cohort study were nondiabetic predominantly Hispanic women delivered at term. Fasting maternal and umbilical vein glucose and insulin concentrations were determined in 29 women with varying early pregnancy body mass index (range, 18.0-54.3) who delivered infants with birthweights ranging from 2800-4402 g. We isolated syncytiotrophoblast microvillous and basal plasma membranes from 33 placentas and determined the expression of GLUT-1 and -9 (Western blot) and glucose uptake (radiolabeled glucose).

RESULTS

Birthweight was positively correlated with umbilical vein glucose and insulin and maternal body mass index. Umbilical vein glucose levels were positively correlated with placental weight and maternal body mass index, but not with maternal fasting glucose. Basal plasma membranes GLUT-1 expression was positively correlated with birthweight. In contrast, syncytiotrophoblast microvillous GLUT-1 and -9, basal plasma membranes GLUT-9 expression and syncytiotrophoblast microvillous and basal plasma membranes glucose transport activity were not correlated with birthweight.

CONCLUSION

Because maternal fasting glucose levels and placental glucose transport capacity were not increased in obese women delivering larger infants, we speculate that increased placental size promotes glucose delivery to these fetuses.